This invention relates to a nuclear fusion process for production of power and of neutrons by bombarding a pellet of fusible material with a plurality of pulsed high energy beams focused in balanced relationship to a region of pellet collision to isentropically compress the pellet to a Fermidegenerate state by thermal blow-off and balanced beam momentum transfer.
The central problem in developing a practical thermonuclear fusion process is that of raising a small mass of nuclearly fusible material such as ionized deuterium or a mixture of deuterium and tritium to the required reaction temperature and maintaining density and temperature long enough for a significant portion of the hot ionized gas to proceed with a nuclear reaction. The temperature required is so high (of the order of 10.sup.8 K..degree.) that no solid state matter can maintain mechanical integrity while in close contact with the reaction. It is necessary either to confine the reacting plasma with a magnetic field or to pulse the reaction so rapidly that inertial forces from rapidly moving high temperature gas can be used to provide the confinement forces for the very short time required.
There have been many attacks on these problems, some of which have produced partial success and great promise for future effectiveness. One of the methods of obtaining thermonuclear fusion under serious investigation at the present time, is laser induced fusion in which pulsed high energy laser beams are focused in balanced relationship to a target position to bombard a small pellet of deuterium-tritium mixture as the pellet traverses the target position. The laser beams are arranged so that part of the dense pellet is isentropically compressed to a high density Fermi-degenerate state by thermal blow-off and beam momentum transfer. Thermonuclear burn is initiated in the central region and propagates outward, igniting the dense fuel. Such a laser induced fusion system is discussed in Review of Modern Physics, Volume 47, No. 1, January, 1975 by F. L. Ribe.
Lasers capable of providing the required high energy beams to make fusion economically practical are under development, but the energy efficiency of such devices is only in a range of about 1-20% at the present time. In addition, a laser beam characteristically has a relatively small momentum available for pellet implosion thereby requiring relatively higher power sources in the case of laser beams.
Relative to laser technology, particle beam technology is an old and well developed art offering several advantages not currently available with lasers. The most important of these is that electron and ion beams can be produced at 80-90% energy efficiency. Additional advantages offered by particle beams are short wave lengths, high momentum and additional fusible mass free from contaminants. The momentum and fusible mass of particle beams if used for bombarding a pellet could reduce the ablation loss and result in leaving a larger fraction of the pellet available for the fusion reaction. Inspite of the numerous known advantages already available in particle beam technology, it has not previously been employed for delivering energy for igniting a nuclear fusion pellet, probably because of the difficulty in focusing a dense beam of charged particles of one sign in order to achieve the requisite control and symmetry in the pellet collision and imploding pressure. One approach to particle beam fusion is described in Hirsch U.S. Pat. No. 3,530,036, but it is limited by reason of space charge induced expansion.
It has been proposed that charged particle beams can be neutralized by including a quantity of a gas at the reaction space, and this procedure is sometimes referred to as "gas neutralization". In the gas neutralization process, the particles of the beam produce ionization of the gas, and for a positively charged particle beam, the resultant electrons will to some degree neutralize the charged particles. However, this leaves the positive gas ions which also require neutralization. Also, the electrons from the ionization tend to overshoot in the beam producing oscillation and instability.
It is an object of the present invention to provide a new and improved process and apparatus which overcomes the disadvantages of the prior processes and apparatus.